Dragline buckets

ABSTRACT

A dragline bucket comprising: a floor having a ground engaging leading edge, a rear wall extending upward from said floor and spaced rearward from said leading edge, and two spaced apart side walls extending upward from said floor and forward from said rear wall, the upper edges of said rear wall and said side walls defining an open top and the height from said floor of at least a portion of said side walls forward of said rear wall being substantially less than the height of said side walls adjacent said rear wall.

FIELD OF THE INVENTION

This invention relates to dragline buckets.

BACKGROUND OF THE INVENTION

Although there are many factors affecting the productivity of adragline, the efficiency and effectiveness of the bucket during the digcycle (that is, fill carry and dump) has a big influence on the overallproductivity of the dragline. Previous inventions have been aimed atincreasing the efficiency and effectiveness of the bucket during thefill component of the dig cycle. However, there is room for furtherimprovement in that area and there is also room for improvements inother areas.

A large amount of energy is required to pull a dragline bucket throughspoil during the fill phase and to carry the bucket and the spoil to thedump site. Some of the energy is used in moving the bucket itself andsome to moving the spoil contained in the bucket. Thus it is desirableto maximise the ratio of mass of spoil, that is, the payload, to themass of the bucket. It is also desirable to retain as much of the spoilas possible which has entered the bucket during the fill phase throughthe carry phase to the dump site. The present invention is aimed atproviding a dragline bucket which is more efficient than previouslyknown buckets at least in some circumstances.

DISCLOSURE OF THE INVENTION

With the foregoing in view, the invention in one aspect resides broadlyin a dragline bucket comprising:

a floor having a ground engaging leading edge, a rear wall extendingupward from said floor and spaced rearward from said leading edge, andtwo spaced apart side walls extending upward from said floor and forwardfrom said rear wall, the upper edges of said rear wall and said sidewalls defining an open top and the height from said floor of at least aportion of said side walls forward of said rear wall being substantiallyless than the height of said side walls adjacent said rear wall.

In another aspect, the invention resides broadly in a dragline bucketcomprising:

a floor having a ground engaging leading edge;

a rear wall extending upward from said floor and spaced rearward fromsaid leading edge;

two spaced apart side walls extending upward from said floor and forwardfrom said rear wall, the upper edges of said rear wall and said sidewalls defining an open top; and

a lifting arch operatively connected to said floor and/or said sidewalls forward of said rear wall, said leading edge and said lifting archdefining a mouth through which spoil may enter, the height from saidfloor of at least a portion of said side walls between said rear walland said lifting arch being substantially less than the height of saidrear wall from said floor.

In yet another aspect, the invention resides broadly in a draglinebucket comprising:

a floor having a ground engaging leading edge;

a rear wall spaced from said leading edge and extending upwards fromsaid floor and curving forward at opposite sides of its centre to meettwo spaced apart side walls also extending upward from said floor andforward from said rear wall, the upper edges of said rear wall and saidside walls defining an open top.

In yet another aspect, the invention resides broadly in a draglinebucket comprising:

a floor having a ground engaging leading edge;

a rear wall spaced from said leading edge and extending upwards fromsaid floor and curving forward meet two spaced apart side walls alsoextending upward from said floor and forward from said rear wall, theupper edges of said rear wall and said side walls defining an open top;and

a lifting arch operatively connected to said floor and/or said sidewalls forward of said rear wall, said leading edge and said lifting archdefining a mouth through which spoil may enter.

Preferably, said side walls and said rear wall terminate in a top railrunning therealong from the lifting arch on one side of the mouth to thelifting arch on the other side of the mouth. However, if desired the toprail could be spaced above the side walls along said portion of lowerheight. In such case, stiffening ribs, gussets or the like may be addedto the side walls if desired to increase its strength.

Preferably, the upper edges of said side walls slope downward at apredetermined angle from the upper edge of said rear wall towards theleading edge of said floor to respective predetermined points. It ispreferred that the predetermined angle is the angle enclosed by astraight line joining the upper edge of the rear wall (at the pointswhere the respective side walls meet the rear wall) to the leading edgeor a point just in front of or just behind the leading edge. Althoughtheoretically the height of the side walls could fall to zero at theleading edge, preferably, the predetermined points are selected toachieve desired energy efficiency while at the same time maintainingsufficient strength. In one presently preferred form, the respectivepredetermined points are where the height of the side walls is abouthalf that of the rear wall (at the points where the respective sidewalls meet the rear wall). In one particularly preferred form, at thatpoint the side walls then curve upwards towards the lifting arch.Typically a plurality of spaced apart teeth will be fitted to the flooralong the leading edge in known manner to improve ground cuttingperformance and in such cases the preferred points to which the straightline referred to above is drawn may vary according to the particularbucket or the particular teeth being used.

In another form, the invention resides broadly in a method of operatinga dragline, including:

providing a dragline having a dragline bucket as previously described;

dragging the bucket through spoil in a forward direction tosubstantially fill a front portion of the bucket and then lifting theground engaging leading edge while continuing dragging in the forwarddirection to tilt the front of the bucket upwards whereby spoilaccumulated adjacent the mouth of the bucket moves towards the rear wallof the bucket;

tilting the bucket to a predetermined carry angle;

lifting the bucket to a desired height;

carrying the bucket to a dump site; and

dumping the spoil at the dump site.

Advantageously, the method according to the invention reduces the amountof load on the drag rope which will be connected to the side walls forpulling the bucket forward.

Terms such as horizontal, vertical, upper, lower, front, rear, side andthe like are used herein for the purpose of describing the inventionfrom the perspective of its normal at rest position and are not intendedto limit the invention to use in any particular orientation. The termspoil is intended to encompass virgin ground and ground which has beendug or stockpiled.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more easily understood and put intopractical effect, reference will now be made to the accompanyingdrawings wherein:

FIG. 1 is a pictorial representation of a conventional dragline bucket;

FIG. 2 is a plan of the dragline bucket of FIG. 1;

FIG. 3 a is a schematic sectional side elevation of a conventionaldragline bucket showing various spoil shear plane lines during the fillphase of a dig cycle;

FIG. 3 b is a schematic sectional side elevation of the dragline bucketof FIG. 3 a showing the initial fill line at the end of the fill phaseof the dig cycle;

FIG. 3 c is a schematic sectional side elevation of the dragline bucketof FIG. 3 a showing the initial fill line and the retained fill lineafter spilling or settling while being lifted at the end of the fillphase;

FIG. 3 d is a schematic sectional side elevation of the dragline bucketof FIG. 3 a at commencement of the carry phase showing the settled fillline;

FIG. 4 is a pictorial representation of a dragline bucket according tothe invention;

FIG. 5 a is a plan of the bucket of FIG. 4;

FIG. 5 b is a side elevation of the bucket of FIG. 4;

FIG. 6 a is a schematic sectional side elevation of the bucket of FIG. 4showing various spoil shear planes during the fill phase of a dig cycle;

FIG. 6 b is a schematic sectional side elevation of the dragline bucketof FIG. 4 towards the end of the fill phase;

FIG. 6 c is a schematic sectional side elevation of the dragline bucketof FIG. 4 showing the initial fill line and the retained fill line afterspilling or settling while being lifted at the end of the fill phase;

FIG. 6 d is a schematic sectional side elevation of the dragline bucketof FIG. 4 during the carry phase showing the settled fill line;

FIG. 6 e is a schematic sectional side elevation of the dragline bucketof FIG. 4 being carried at a greater carry angle than that in FIG. 6 d;and

FIG. 6 f is a schematic sectional side elevation of the dragline bucketof FIG. 4 showing the settled fill line for the carry angle of FIG. 6 ewith the settled line from FIG. 6 d superimposed.

DETAILED DESCRIPTION OF THE DRAWINGS

The dragline bucket 10 illustrated in FIG. 1 has a floor 11 with aground engaging leading edge 12 to which a plurality of spaced apartteeth 13 are fitted in known manner, a rear wall 14 extending upwardfrom the floor and spaced rearward of the leading edge which iscontiguous with two spaced apart side walls 16 and 17 which also extendupward from the floor and forward from the rear wall, the rear wallterminating at its upper edge 18 in a rear top rail 19 and the sidewalls terminating at their upper edges 21 and 22 in side top rails 23and 24 respectively, the top rails defining an open top 26.

A lifting arch 27 is connected to the forward end portions of the sidewalls and to the floor (via the side walls) for connecting the bucket tothe lift cable of the dragline in known manner. It will be appreciatedthat the leading edge 12 together with the side walls and the liftingarch define a mouth 28 through which spoil may enter the bucket. Liftinglugs 29 and 31 are welded to the outer face of the side walls towardsthe rear wall for attaching lifting chains also for connection to thedragline cable. Similarly, drag lugs 32 and 33 are connected to theforward ends of the side walls below the lifting arch for connection tothe drag chain of the dragline in known manner.

It will be appreciated that the top rails 19, 23 and 24 of theconventional bucket all lie in the same plane, that being a planesubstantially parallel to the plane containing the surface of the bodyof the floor of the bucket (which is generally horizontal when at reston level ground). Additionally, the rear wall meets the floorsubstantially at right angles with only a slightly rounded bottom cornerand the rear wall meets the side walls substantially at right angles,the two side walls being substantially parallel and the floor beingsubstantially rectangular.

It is understood in the mining industry that dragline buckets fill inaccordance with what is known as the “shear zone theory”. Under theshear zone theory as illustrated in FIGS. 3 a to 3 d, as the bucketstarts to fill while it is pulled through the virgin spoil an initiallaminar layer 41 of spoil forms over the floor of the bucket. Then, asfilling continues, the virgin spoil immediately in front of the leadingedge shears upwardly over the laminar layer 41 and progressively createsshear zones 42, 43 and so on, until the end of the fill phase of the digcycle to form the mound of spoil 44 as seen in FIG. 3 b. As can also beseen in FIG. 3 b, the mound 44 within the bucket is biased towards theleading edge 12. The bias is due to the bucket “bulldozing” the virginspoil 40 towards the end of the fill phase as evidenced by the uppersurface 46 (shown in phantom) being moved upwards in front of theleading edge. It is believed that particles of clay in the spoil tend tobind together at the front of the bucket thereby increasing the densityof the spoil in that area. The virgin spoil in front of the bucket helpshold the spoil 44 in the bucket.

As the shear zones 42, 43, etc, are formed, the shearing action causesthe spoil towards the front of the bucket to be compacted and hencedenser in front of the peak 47 of the heap 44 then the spoil behind thepeak. Thus, a given volume of spoil forward of the peak will be heavierthen the same volume reward of the peak.

As can be seen in FIG. 3 b, at the end of the drag phase, a portion 47of the heap is above the top rail and a space 52 remains behind themound 44 although in other drag phases, the space may be filled. As thebucket is lifted while still in a horizontal attitude, a movement knownas “nodding” occurs in which the bucket tilts forward and back andcauses spoil from the peak (and forward of the peak) to shear and fallover the leading edge. That lost spoil is typically denser than mostother spoil in the bucket for reasons mentioned previously. The bucketis then titled to a desired carry angle prior to being swung to a dumpsite. The carry angle typically places the floor at 32° to 38° to thehorizontal as generally indicated in FIG. 3 d.

The bucket 110 of the present invention as illustrated in FIG. 4 issimilar to the conventional bucket 10 just described in many respectsand accordingly corresponding numbers will be used to referencecorresponding features except prefaced by a “1”. Thus, it will be seenthat bucket 110 has a floor 111 with a leading ground engaging edge 112having spaced apart teeth 113 mounted thereto, a rear wall 114 extendingupward from the floor and spaced rearward of the leading edge, twospaced apart side walls 116 and 117 also extending upward from thefloor, the upper edge of the rear wall terminating in a rear top rail119 and the upper edges of the side rails 116 and 117 terminating inside tops rails 123 and 124 respectively. A lifting arch 127 is mountedto the side walls and the floor in the same manner as in theconventional bucket shown in FIG. 1 and lifting lugs and drag lugs areprovided in the same manner. However, in the bucket 110, the rear wallcurves outwards from the side walls such that the centre of the rearwall is further behind the leading edge than the ends of the rear wall.It will also be seen that the rear wall is higher in the centre andcurves downwards to the points where it meets the respective sidewalls.

It will also be seen that the height of the side walls of the bucket 110from the floor is not constant as in conventional bucket 10, but ratherthe upper edges slope forward from the rear top rail at an angle α to astraight line drawn from the rear top rail to the ground engagingleading edge for a point approximately halfway along the length of thefloor. At that point, the side walls are approximately half the heightof the rear wall and from there, the side walls curve upwardly in an arctowards the top of the lifting arch in a manner selected to achievesufficient structural integrity. Testing has demonstrated that theoptimum carry angle of the dragline bucket, represented by the anglebetween the floor 111 and the horizontal to be equal to or greater thanthe angle α as will be discussed in more detail later.

As can be seen in FIG. 6 a, the shear zone theory applies to the initialfill stages in the same manner as previously described in relation toconventional buckets in relation to shear zones 141, 142, 143 and so on.However, when the bucket is filled according to the method broadlydescribed earlier, the peak 147 of the mound 144 is further forward thanin the conventional bucket relative to the leading edge with more spoilin the zone of higher density. Moreover, as the bucket is titled furtherback as illustrated in FIG. 6 c, spoil therein settles to the generalshape of the mound 148 shown therein. One advantage of progressivelyangling the bucket 110 from the horizontal to the desired carry angleduring the fill phase is that more of the filled spoil is retainedduring the fill phase and in the transition between the fill phase andthe carry phase (that is the initial lift after filling) than withconventional buckets using conventional digging methods. Thus, bucketsconstructed according to the present invention and used according to themethod described earlier are less likely to suffer the spoil losses dueto “nodding” and will have a greater ratio of retained spoil payload tobucket weight than conventional buckets. It is also believed thatbuckets according to the present invention have higher drag efficiencydue to less drag friction.

In use, bucket 110 commences digging in the horizontal attitudeillustrated in FIG. 6 a and after a mound forms to the level 147 shownin FIG. 6 b, the bucket is tilted or rolled back slightly by lifting thelifting arch and thus the leading edge 112. As the bucket moves, thearch is lifted higher thus tilting the bucket back further to thedesired carry angle as it fills to the level 148 shown in FIG. 6 c andthen as the bucket is lifted further for the carry phase, the moundsettles to the form 149 shown generally in FIG. 6 d. Under this method,the face of the virgin spoil will tend to form an arc and the bucketwill tend to follow the arc during each dig cycle. Depending on the typeof spoil being dug, the bucket can be tilted further back and be carriedat a steeper carry angle to prevent loss of filled spoil over theleading edge as shown by levels 150 and 151 in FIGS. 6 e and 6 f. itwill be appreciated that the reduced height of the side walls of thebucket results in a decrease in energy consumption during the fill phasebecause spoil movement in the fill phase is not as constrained by theside walls as in previously known buckets.

The foregoing description has been given by way of illustrative exampleof the invention and all modifications and variations thereto as wouldbe apparent to persons skilled in the art are deemed to fall within thebroad scope and ambit of the invention as defined by the appendedclaims.

1-14. (canceled)
 15. A dragline bucket comprising: a floor having aground engaging leading edge, a rear wall extending upward from saidfloor and spaced from said leading edge, and two spaced apart side wallsextending upward from said floor and forward from said rear wall towardssaid leading edge, the upper edges of said rear wall and said side wallsdefining an open top and the height of said rear wall and said sidewalls from said floor decreasing away from about the centre of said rearwall to at least respective predetermined points along said side walls.16. A dragline bucket according to claim 15 wherein said predeterminedpoints are located about midway between said rear wall and said leadingedge.
 17. A dragline bucket comprising: a floor having a ground engagingleading edge, a rear wall extending upward from said floor and spacedfrom said leading edge, and two spaced apart side walls extending upwardfrom said floor and forward from said rear wall towards said leadingedge, the upper edges of said rear wall and said side walls defining anopen top and at least a portion of the upper edge of each said side walllying in a plane containing a line extending from about the centre ofthe upper edge of said rear wall to about said leading edge.
 18. Adragline bucket according to claim 17 wherein the portion of the upperedge of each side wall lying in said plane extends from said rear wallto a predetermined point between said rear wall and said leading edge.19. A dragline bucket according to claim 18 wherein said predeterminedpoint is a point where the height of said side walls is about half theheight of said rear wall.
 20. A dragline bucket according to claim 15wherein said side walls and said rear wall terminate in a top railrunning along their respective upper edges or formed by their upperedges.
 21. A dragline bucket according to claim 15 including a liftingarch operatively connected to said floor and/or said side walls forwardof said rear wall, said leading edge and said lifting arch togetherdefining at least in part a mouth through which spoil may enter.
 22. Adragline bucket according to claim 21 wherein said side walls and saidrear wall terminate in a top rail extending from the lifting arch on oneside of the mouth to the lifting arch on the other side of the mouth.23. A dragline bucket according- to claim 21 including generallyhorizontal top rails spaced above the upper edges of said side wallsrespectively along a substantial portion thereof.
 24. A dragline bucketaccording to claim 21, wherein the side walls curve upwards from saidpredetermined point towards said lifting arch.
 25. A dragline bucketaccording to claim 17 wherein said side walls and said rear wallterminate in a top rail running along their respective upper edges orformed by their upper edges.
 26. A drag line bucket according to claim17 including a lifting arch operatively connected to said floor and/orsaid side walls forward of said rear wall, said leading edge and saidlifting arch together defining at least in part a mouth through whichspoil may enter.
 27. A dragline bucket according to claim 26 whereinsaid side walls and said rear wall terminate in a top rail extendingfrom the lifting arch on one side of the mouth to the lifting arch onthe other side of the mouth.
 28. A dragline bucket according to claim 26including generally horizontal top rails spaced above the upper edges ofsaid side walls respectively along a substantial portion thereof.
 29. Adragline bucket according to claim 26, wherein the side walls curveupwards from said predetermined point towards said lifting arch.
 30. Adragline bucket comprising: a floor having a ground engaging leadingedge; a rear wall spaced from said leading edge and extending upwardsfrom said floor and curving forward from its centre on both sidesthereof to meet two spaced apart side walls also extending upward fromsaid floor and forward from said rear wall, the upper edges of said rearwall and said side walls defining an open top.
 31. A dragline bucketaccording to claim 30 wherein said side walls and said rear wallterminate in a top rail running along their respective upper edges orformed by their upper edges.
 32. A dragline bucket according to claim 30including a lifting arch operatively connected to said floor and/or saidside walls forward of said rear wall, said leading edge and said liftingarch together defining at least in part a mouth through which spoil mayenter.
 33. A dragline bucket according to claim 32 wherein said sidewalls and said rear wall terminate in a top rail extending from thelifting arch on one side of the mouth to the lifting arch on the otherside of the mouth.
 34. A dragline bucket according to claim 32 includinggenerally horizontal top rails spaced above the upper edges of said sidewalls respectively along a substantial portion thereof.
 35. A draglinebucket according to claim 32, wherein the side walls curve upwards fromsaid predetermined point towards said lifting arch.
 36. A method ofoperating a dragline, including: providing a dragline having a draglinebucket as claimed in claim 15, including: dragging the bucket throughspoil in a forward direction to substantially fill a front portion ofthe bucket and then lifting the ground engaging leading edge whilecontinuing dragging in the forward direction to tilt the front of thebucket upwards whereby spoil accumulated adjacent the mouth of thebucket moves towards the rear wall of the bucket; tilting the bucket toa predetermined carry angle; lifting the bucket to a desired height;carrying the bucket to a dump site; and dumping the spoil at the dumpsite.